Chronic obstructive pulmonary disease (COPD) is a serious progressive lung disease which makes it harder to breath. It currently affects over fifteen million people in the United States alone and is currently a leading cause of death in the country. The overwhelming primary cause of COPD is inhalation of cigarette smoke, responsible for over 90% of COPD cases. The economic and social burden of the disease is both substantial and increasing.
FIG. 1 depicts a healthy set of lungs 10 in an individual. A wind pipe or trachea 12 connects the nose (not shown) and mouth (not shown) to the lungs 10. As air flows in through the nose and mouth of an individual, the trachea 12 transports the air to the lungs 10 for respiratory functions. The trachea 12 divides into the left 14 and right 16 bronchus stems, which further divide into a plurality of bronchi 18, bronchioles 20, and eventually, terminate in a plurality of alveoli 22. The alveoli 22 are small air sacs which enable gas exchange with the individual's blood stream. That is, they permit oxygen diffusion into the blood stream, and receive and expel CO2 during exhalation.
COPD includes emphysema. As shown in FIG. 2A, emphysema may be characterized by the destruction of lung parenchyma 24, the functioning parts of the lungs 10. The parenchyma 24 includes the alveoli 22 walls, bronchioles 20, and the bronchi 18. Destruction of these tissues results in progressively increasing shortness of breath called dyspnea. As it worsens, emphysema turns the healthy alveoli 22, clustered like bunches of grapes, into large, irregular pockets with gaping holes in their inner walls, as shown in FIG. 2B. This reduces the surface area of the lungs and, in turn, the amount of oxygen that reaches an individual's blood stream.
Destruction of the lung parenchyma may also lead to loss of elastic recoil and tethering (i.e., ability to hold open walls of airways, including the bronchioles 20, leading to the alveoli 22 throughout much of inhalation and expiration), which maintains airway patency. Unlike larger lung airways, the bronchioles 20 are not supported by cartilage and thus have little intrinsic support. As a result, the bronchioles 20 are susceptible to collapse or reduction in diameter when destruction of tethering occurs, particularly during exhalation. The collapse of airways may prevent air in the alveoli 22 from escaping during exhalation. A significantly reduced diameter airway 26 connecting to an alveoli 22 is depicted in FIG. 2B. This trapped gas in the alveoli 22 may lead to hypercapnia (high levels of CO2 in the blood stream) and acidosis (lowering of pH levels), which are correlated to mortality in COPD patients.
One existing approach to treat emphysema is performing lung volume reduction surgery, which removes or kills a portion of a diseased lung to allow greater expansion of remaining lung tissue. However, this approach poses a substantial risk due to its invasive nature. It may, therefore, be beneficial to provide a less-invasive technique for treating emphysema, or other lung conditions including asthma.